The present invention relates to a sliding component that is used, for example, in a compressor for an air conditioning system, and to a compressor.
Lubrication of sliding components constituting an internal mechanism of a compressor is normally carried out by forming lubricating oil held in the compressor into mists with a refrigerant gas (e.g., a refrigerant gas of chlorofluorocarbon gas or the like) circulated in the operating compressor, and carrying the oil in the mist form to each sliding portion. However, in the case of restarting the compressor after it has been left unoperated for a long time, the lubricating oil adhered to the sliding portion may be washed away by the refrigerant gas.
For example, in a swash plate compressor, each piston is connected through shoes to a swash plate, and reciprocated in a cylinder bore by rotation or sliding of the swash plate. The swash plate and the shoes are slid before the lubricating oil reaches the sliding surfaces thereof immediately after the compressor is started. Moreover, before the lubricating oil reaches the sliding surfaces of the swash plate and the shoes, a gaseous refrigerant reaches the sliding surfaces and washes the lubricating oil remaining on the sliding surfaces. Accordingly, the swash plate and the shoe are slide under a dry sliding condition of no lubricating oil immediately after the compressor is started.
Therefore, during the period (about one minute) between returning of the refrigerant gas to the compressor and starting of mist formation of the compressor, the sliding portion, which needs lubricating with the compressor in operation, is subjected to a state of inadequate lubrication. Thus, the conventional art has presented technologies for reliably lubricating the sliding portion in such a period of an insufficient lubricating oil quantity.
Examples presented in order to improve sliding characteristics of the swash plate and the like include a method of forming an Ni—P plated film on a sliding surface by electroless plating and a method of forming an Al sprayed film on a surface of a swash plate made of iron. Furthermore, Japanese Laid-Open Patent Publication No. Hei 11-13638 discloses a method of forming a plated layer of tin, copper or the like on a surface of a swash plate made of an iron- or aluminum-based substrate material (i.e., surface slide-contacting a shoe), and forming a slide-contacting layer made of a polyamide-imide resin, and a solid lubricant (molybdenum disulfide, graphite or the like) on the plated layer.
However, the method of forming the Ni—P plated film or the Al sprayed film on the sliding surface of the swash plate has provided no sufficient sliding characteristics. The method of forming the slide-contacting layer made of the polyamide-imide resin and the solid lubricant, disclosed in Japanese Laid-Open Patent Publication No. Hei 11-13638, has provided better sliding characteristics compared with the method of forming the Ni—P plated film, but still not sufficient. Recently, carbon dioxide has attracted attention as a refrigerant of the compressor. However, use of the carbon dioxide as a refrigerant results in a greater increase in a compression load applied on the swash plate through the piston compared with the use of chlorofluorocarbon refrigerant, making a sliding environment severer. Thus, there is a need for improvement of sliding characteristics.